US 7975491 B2
A heat exchange system selectably controls the temperature of a fluid being delivered to a patient's body by a pump device. The heat exchange system includes a thermal element and a heat exchanger that is removably coupled under pressure to the thermal element. The heat exchanger includes a first half made from thermally conductive material that correspondingly mates with the thermal element, a second half made from thermally conductive material opposite the first half, and an internal heat exchange zone existing between the first half and the second half, wherein fluid flows therethrough. The thermal element of the heat exchange system may controllably and safely warm and/or cool the fluid prior to delivery.
1. A heat exchange system for a pump device, comprising:
a. a thermal element; and
b. a heat exchanger removably coupled under pressure to said thermal element comprising:
a first half comprising thermally conductive material correspondingly mating with said thermal element;
a second half comprising thermally conductive material opposite said first half; and
an internal heat exchange zone existing between said first half and said second half, wherein fluid flows therethrough.
2. The heat exchange system of
3. The heat exchange system of
4. The heat exchange system of
5. The heat exchange system of
6. The heat exchange system of
7. The heat exchange system of
8. The heat exchange system of
9. The heat exchange system of
10. The heat exchange system of
11. The heat exchange system of
12. The heat exchange system of
13. The heat exchange system of
14. The heat exchange system of
15. The heat exchange system of
16. The heat exchange system of
17. The heat exchange system of
18. The heat exchange system of
19. A heat exchange system for a pump device, comprising:
a. a cooling element comprising at least one thermoelectric cooler creating at least one cooling point on said cooling element; and
b. a heat exchanger removably coupled under pressure to said cooling element comprising:
a first half constructed from thermally conductive material correspondingly mating with said cooling element;
a second half constructed from thermally conductive material opposite said first half; and
an internal heat exchange zone existing between said first half and said second half, wherein fluid flows therethrough.
20. The heat exchange system of
21. The heat exchange system of
a heating platen;
a first surface that substantially mates with said first half of said heat exchanger; and
a second surface in communication with said at least one thermoelectric cooler.
22. The heat exchange system of
23. The heat exchange system of
24. The heat exchange system of
25. A heat exchange system for a pump device, comprising:
a. a heating and cooling element comprising at least one thermoelectric heat pump selectably creating at least one heat point or at least one cooling point on said heating and cooling element; and
b. a heat exchanger removably coupled under pressure to said heating and cooling element comprising:
a first half constructed from thermally conductive material correspondingly mating with said cooling element;
a second half constructed from thermally conductive material opposite said first half; and
an internal heat exchange zone existing between said first half and said second half, wherein fluid flows therethrough.
26. The heat exchange system of
27. The heat exchange system of
28. The heat exchange system of
a heating platen;
a first surface that substantially mates with said first half of said heat exchanger; and
a second surface in communication with said at least one thermoelectric heat pump.
29. The heat exchange system of
This application is a continuation-in-part of U.S. patent application Ser. No. 11/082,260 filed Mar. 17, 2005, which is incorporated by reference in its entirety herein.
This invention was made possible at least in part with the assistance of US Grant No. DAMD 17-02-01-0700 awarded by the United States Army, and the government may have certain rights therein.
The present invention is directed to an infusion device having a disposable cartridge for warming and/or cooling fluid that connects with a pump housing and allows for simple, accurate control of infusion flow rates and/or infusion pressures.
Fluid required in treating a patient must often be stored in comparatively cool to cold temperatures with respect to the patient's body temperature. This often refrigerated storage is necessary to preserve the fluids in a state so the function and integrity of the fluid is maintained. Fluids such as blood and other bodily fluids are typically stored at hypothermic temperatures ranging from 2° to 20° Celsius. Therefore, when introducing fluids into the patient's body it is often necessary to heat the fluid to an appropriate temperature not only to prevent any rapid decrease in the patient's body temperature, but also to ensure that the fluid being introduced can function as needed. It is known that the injection of cold fluids into a patient's body can create a major source of conductive heat loss within the patient, often placing the patient at further risk by cooling, too quickly or, to a temperature where physiological damage can occur.
In heating or warming the fluid, however, care must be taken to ensure that the heating itself does not create a further complication. For instance, if blood reaches a certain temperature then hemolysis, the destruction or severe degradation, of the blood cells can occur. Likewise, if the fluid is heated too high and then introduced into the patient's body, physiological damage resulting from exposure to excessive temperatures such as burns or other such scarring can occur. Heating the fluid in bulk form usually requires the application of too intense a heat source in order to heat the entire fluid with any level of time efficiency. Likewise, heating the fluid over a prolonged period of time can lead to increased exposure of the material to the environment creating risks of contamination.
Getting the fluid into the patient requires adjustable flow so that the proper amount of fluid depending upon the need is provided to the patient. Combining the fluid delivery means with the proper and efficient heating of the fluid is crucial to the proper delivery of fluid to the patient. The prior art contains systems for warming fluids as they are infused into a patient. The manner in which the fluids are heated within these systems varies and can be accomplished via convection or conduction. An example of a system which poses clinical problems heats the fluid being delivered to the patient via exposure to a heated fluid, such as water. Such systems are usually cumbersome, require frequent cleaning, and can pollute the clinical environment through the introduction of an additional substance—the heating liquid. Such a system often places a conduit through a liquid such as water, which is then heated, and the fluid to be delivered to the patient is drawn through the conduit thereby increasing the temperature of the fluid to be delivered. Such a system can be deleterious to a sterile environment and may not be properly transported. Furthermore, these systems also have large mass, which require significant power to heat that mass yielding a significant time to achieve that temperature, or achieve a stasis when a cold mass (like a bag of chilled fluid) is introduced. An additional problem to be avoided is the danger to the patient caused by current leakage in the system circuitry and specifically the circuitry used to achieve the warming characteristics that may be in close contact to the blood being infused to the patient. Capacitive coupling, the transfer of energy from one element to another by means of mutual capacitance, could possibly cause enough current leakage to the heating system, and, potentially, to the patient and cause electric shock. It is, therefore, important to reduce the amount of capacitive coupling between the heating system and the heating exchanger, thus reducing the potential for current leakage and reducing the risk of causing electric shock to the patient, while at the same time creating efficient heating of the blood.
Moreover, during some fluid infusion procedures it is beneficial to adjust the temperature of the patient's body either warmer or cooler. As such, it is extremely beneficial to have an adjustable in-line fluid warming or cooling system so that the proper temperature can be regulated. In instances of massive or emergent fluid loss, it is often necessary to infuse (and sometimes recover and re-infuse) extremely large amounts of fluid into the patient's body. In such instances, traditional fluid heating systems often place the fluid at risk by exposure to temperatures which could damage the fluid because the fluid must be heated so rapidly. Furthermore, whereas existing patient cooling methods include practices such as externally applying cooling blankets, it will be beneficial to provide a system that more efficiently and rapidly cools a patient's core body temperature. Such problems remain largely unsolved by the art; and the need for better in-line fluid infusers is abundant.
Similarly, studies have shown that symptoms and harmful effects of certain conditions may be reduced by inducing hypothermia. For example, it has been demonstrated that circulating cooled blood before or during ischemia reduces the infarct size or slows the effects caused by infarction. Similarly, other studies show that cooling patients after suffering an acute stroke reduces metabolism and inflammation, both factors affecting ischemia induced by stroke. Thus, there also exists a need for a means to accurately cool fluid, like blood, and control flow rates of the cooled fluid.
When introducing fluid into a patient's body (e.g., the circulatory system) it is crucial that air not be introduced into the patient's body as well. Introduction of air or air bubbles into a patient's body (e.g., the circulatory system) can cause extremely deleterious effects. Air embolisms can occur if air accumulates in a patient's blood stream resulting in cardiac arrhythmias, stroke, or pulmonary infarct. Any of these potential infirmities can be life threatening and need to be minimized in situations where high volumes of fluid are being infused. It is therefore extremely important that during infusion of fluid that both the monitoring of air in the infusion system occurs to prevent introduction into the patient's body.
Devices in the prior art seeking to warm fluid for infusion into the body often suffer from very specific problems. For example, the heater system described in U.S. Pat. No. 3,590,215 issued to Anderson et al. uses regions of differing heat which the fluid encounters as it progresses through the system. Specifically, the heating element or elements described in Anderson et al. diminishes the heat in the material warming the fluid from a hottest temperature where the fluid enters the heat exchanger to a coolest temperature where the fluid exits the heat exchanger. Such a configuration not only makes it difficult to regulate the temperature of the fluid as the flow rate changes, but it also runs the risk of having to expose the fluid to temperatures above which the fluid should be exposed to, running the risk of damaging the fluid.
Likewise, the serpentine fluid flow path described in Anderson et al. creates the typical laminar type flow seen in most heat exchanger systems. For example. U.S. Pat. No. 5,245,693 to Ford et al. describes a serpentine flow pattern which is long compared to its width and wider compared to its depth. This type of flow is consistent with a non-turbulent laminar type flow path. A non-turbulent flow path requires additional heat energy to be introduced into the fluid system or longer exposure to the heating in order to increase the temperature of the fluid system uniformly to a desired temperature.
In addition to heating the fluid efficiently, a variety of clinical circumstances, including massive trauma, major surgical procedures, massive burns, and certain disease states such as pancreatitis and diabetic ketoacidosis can produce profound circulatory volume depletion, either from actual blood loss or from internal fluid imbalance. In these clinical settings, it is often necessary to infuse blood or other fluids rapidly into a patient to avert serious consequences.
Intravenous infusion rates may be defined as either routine, generally up to about 999 cubic centimeters per hour, or rapid, generally between about 999 cubic centimeters per hour and about 90,000 cubic centimeters per hour (1.5 liters per minute) or higher. Most existing infusion pumps are designed for medication delivery and are limited in their performance to the routine range of infusion rates. Such pumps are not capable of rapid intravenous infusion. Although some prior infusion systems can deliver rapid infusion, those prior rapid infusion devices are physically large, complex systems that require dedicated operation by skilled technicians. For example, U.S. Pat. No. 6,942,637 issued to Cartledge et al. describes a rapid infusion system having a differential drive that interacts with multiple motors to achieve the variable pumping rates desired. U.S. Pat. No. 6,942,637 specifically describes a differential drive that includes, among other components, multiple motors, such as a high speed motor and a stepper motor, and a combination of gears mechanically linking the multiple motors to a common drive shaft.
In other uses, a fluid pump system may be used for fluid delivery during certain surgical procedures, such as arthroscopic surgeries, to distend the area of operation. For example, saline solution is infused into the joint during an arthroscopy to expand the joint and clear the surgical field of view. However, current technologies are deficient in allowing the control of both the pressure and temperature of the fluid so as to not cause excessive cooling or warming of the area.
Accordingly, what is needed is a pump device for variably controlling fluid flow rates, fluid flow pressures, and fluid temperatures that is compact and easily operated by medical personnel in the course of their other duties. What is also needed is a low-to-high speed pump device that may heat or cool fluid efficiently and safely, that utilizes a sterile, disposable fluid containment system that can be readily attached and removed from a separate pumping mechanism.
Described is a system for controlling the flow and temperature of a fluid being infused into a patient's body while the infusion is taking place. Such a pump system is also referred to as an, an infusion system, or an in-line heating or cooling infusion system. The system also provides for improved monitoring of air in the infusion system such to prevent the introduction of air into the patient's body receiving the fluid infusion. The pump system also provides variable flow rates and flow pressures that may be dynamically controlled by way of an electronically controlled motor, that serve a vast amount of infusion needs. The pump system may also be controlled through a simple user interface to a system having stored logic and data collection capabilities that allows for simple and accurate control of the system. Improved heat exchange efficiencies through advantageous construction and circuitry of the system components are also provided for while also reducing the risk of sustaining electric shock by the patient. The components of the disposable cartridge align with their respective component mates on the pump housing, so as to make attaching the disposable cartridge to the pump housing and operation simple and effective.
More specifically, the system may include a heat exchange system for a pump device that may include a thermal element and a heat exchanger removably coupled under pressure to the thermal element. The heat exchanger may have a first half formed from a thermally conductive material and correspondingly mating with the thermal element, a second half made from a thermally conductive material opposite the first half, and an internal heat exchange zone existing between the first half and the second half, wherein fluid flows therethrough.
In another example of the pump system provided for, a heat exchange system for a pump device includes a heating and cooling element, as a single component, and a heat exchanger removably coupled under pressure to the heating and cooling element. The heating and cooling element includes at least one thermoelectric heat pump that may selectably create at least one heat point or at least one cooling point on the heating and cooling element.
A disposable heat exchange cartridge and pump device for use during fluid infusion into a patient's body is described. The disposable heat exchange cartridge is removably coupled to an infusion pump device which provides not only the energy or power required to heat or cool the fluid being infused, but also provides, the flow generating pump and mechanisms for monitoring and regulating particular aspects of the fluid pumping system. More specifically, the disposable heat exchange cartridge may include a heating element disposed in the pump device by means that increase the efficient transfer of heat energy, while also providing safe and simple operation of the system. Alternatively, the disposable heat exchange cartridge may include a cooling element similarly disposed to cool the temperature of the fluid. Additionally, the disposable heat exchange cartridge has components that are advantageously aligned with their respective component mates on the pump system, allowing for simple attachment and detachment. Furthermore, the pump device includes a simple user interface that allows for accurate control of the pump device and the collection of operation-related data. In this description of the invention, reference will be made to the embodiments shown in
One aspect described herein is a heat exchange system for a pump device that includes a thermal element and a heat exchanger removably coupled under pressure to the thermal element. The heat exchanger includes a first half formed from a thermally conductive material and correspondingly mating with the thermal element, a second half made from a thermally conductive material opposite the first half, and an internal heat exchange zone existing between the first half and the second half, wherein fluid flows therethrough.
In one embodiment described herein, the thermal element may include a resistive heater, a radiant heater, an induction-based heater, a microwave heater, a thermoelectric heat pump, a thermoelectric cooler, or the like. In one embodiment including a heating element, the heating element may include a plurality of power resistors electrically connected to limit capacitive coupling and to create a plurality of heat points on the heating element. More specifically, the heating element may include about three to five power resistors, and in some embodiments it may include five power resistors. The power resistors may have a total resistance between about 8 ohms to about 12 ohms, and in some embodiments they may have a total resistance of about 10 ohms. The plurality of power resistors may be connected to limit current leakage from the heating element to a patient to about 10 microamperes or less and to limit capacitance coupling to about 100 picofarads or less.
In an embodiment having a heating element as described herein, the heat exchange system may include a thermally conductive thermal pad positioned between the heating element and the heat exchanger. The heating element may further include a heating platen and at least one ceramic insulator interposed between the plurality of resistors and the heating platen, wherein the heating platen has a first surface that substantially mates with the first half of the heat exchanger and a second surface in communication with the plurality of resistors. The heating platen may be formed from aluminum alloy, copper, gold, silver, carbon foam, a ceramic-based material, or the like. The ceramic insulator may be formed from aluminum oxide, or the like, in some embodiments. Further, the ceramic insulator may have a thermal conductivity of about 20 W/m-K or greater, and of about 30 W/m-K or greater in other embodiments. Thermal bonding compound may be interposed between the second surface of the heating platen and the ceramic insulator, and interposed between the ceramic insulator and the plurality of resistors. The thermal pad may be attached to the first surface of the heating platen or to the heat exchanger.
In one embodiment described herein, the heat exchanger is formed from at least two symmetric units fixed together. In alternate embodiments, the heat exchanger may be formed from a single unit. The heat exchanger may be formed from aluminum alloy, copper, gold, silver, carbon foam, a ceramic-based material, or the like, and in one specific embodiment, the heat exchanger is formed from aluminum. The internal heat exchange zone of the heat exchanger may include a first and second plurality of overlapping fins, creating a substantially uniform flow path depth, wherein each the fin has a ratio of height to width of at least 1:2, whereby fluid enters the heat internal heat exchange zone and fills the cavity across the width of the heat exchange zone prior to flowing through the heat exchange zone and out of the heat exchange zone.
In one embodiment described herein, heat exchanger may have an exposure surface that is a broad surface area in communication with the thermal element, and which may be between about 20 square inches and about 100 square inches, and between about 30 square inches and about 45 square inches in some embodiments. The heat exchanger may be removably coupled to the thermal element by an engaging actuator which actuates at least one clamping mechanism, creating at least 100 pounds of compressive force between the heat exchanger and the thermal element. The thermal element may be integrated within a pump housing and the heat exchanger may be integrated within a disposable cartridge.
One aspect described herein is a heat exchange system for a pump device that includes a cooling element and a heat exchanger removably coupled under pressure to the cooling element. The cooling element includes at least one thermoelectric cooler that creates at least one cooling point on the cooling element.
In one embodiment, the thermoelectric cooler or coolers are a pettier thermoelectric cooler comprising an array of n-type and p-type semiconductors disposed between two ceramic insulators. The cooling element may further include a heating platen and a thermally conductive thermal pad positioned between the cooling element and the heat exchanger. The cooling element may be integrated within a pump housing. The cooling element may cool and substantially maintain fluid at a temperature between about 0° Celsius and about 37° Celsius, and in some embodiments between about 4° Celsius and about 1.5 Celsius. In one embodiment the heat exchange system may additionally include a heating element having a plurality of power resistors connected to create low capacitive coupling and to create a plurality of heat points on the heating element, wherein the heating element is interchangeable with the cooling element.
One aspect described herein is a heat exchange system for a pump device that includes a heating and cooling element, as a single component, and a heat exchanger removably coupled under pressure to the heating and cooling element. The heating and cooling element includes at least one thermoelectric heat pump that may selectably create at least one heat point or at least one cooling point on the heating and cooling element.
In one embodiment described herein, the thermoelectric heat pump may be a peltier thermoelectric heat pump. The thermoelectric heat pump or pumps may selectably sink or source heat from or to the heat exchanger by reversing the flow of current through the peltier thermoelectric heat pump. In one embodiment, a plurality of thermoelectric heat pumps may selectably create a plurality of heat points or a plurality of cooling points on the heating and cooling element. The heating and cooling element may further include a heating platen and a thermally conductive thermal pad positioned between the heating and cooling element and the heat exchanger.
In one embodiment, a heat exchanger 101, as depicted in
The fluid then passes into the heat exchanger 101 via the exchanger inlet port 106 at the lower aspect of the heat exchanger. In the above described embodiment including a pump outflow tube 109, the pump outflow tube 109 couples with the exchanger inlet port 106 of the heat exchanger. After the fluid passes through the turbulent environment established by the heat exchanger 101, it exits via the exchanger outlet port 107 located at a position opposite the exchanger inlet port 106 at the upper aspect of the heat exchanger 101. At this point, the fluid for infusion has undergone its warming or cooling and the desired temperature has been reached. A heat exchanger temperature sensor 287, as described in reference to
The fluid exits the heat exchanger 101 via the exchanger outlet port 107, and then enters the air-trap 110 at about the mid-point along the long-axis of the air-trap 110. Fluid flows out of the air-trap 110 and through a third t-junction, which serves as the fluid outflow pressure junction 135. Similar to the inflow pressure junction and pump outflow pressure junction, the fluid outflow pressure junction 135 and another air chamber may communicate with sensors on the pump device to measure the pressure of the infusion fluid prior to delivery to the patient. The fluid outflow pressure junction 135 assists in allowing for the control of the infusion pressure so pressure can either be substantially maintained at a pre-defined pressure, or kept within a pre-defined maximum or minimum limit. Next, prior to delivery to the patient, the fluid is sensed by the outflow bubble detector 112 and subsequently the outflow temperature sensor 261, aligning with another bubble detector interface 230, in the same manner as is described for the inflow bubble detector and inflow temperature sensor, described above and further in reference to
A detailed description of the heat exchanger 101 requires reference to
It is appreciated that in other embodiments the heat exchanger 101 may be constructed so as to cause a discrete flow path, rather than a disruptive, laminar flow path, as previously described. For example, a heat exchanger configured in this manner may not have fins, but instead may provide a distinct path by a series of flow walls, for example, in a serpentine-type flow path, so as to increase exposure of the fluid to the thermally conductive heat exchanger. It is further appreciated that other means of directing flow through a heat exchanger, so as to efficiently facilitate heat transfer, as are known in the art, may be employed.
A further benefit achieved by creating the heat exchanger 101 from the same mold is that all surface areas in which the infusion fluid contacts will be the same highly conductive material, such as anodized aluminum, as further described below. Rather than creating only the half of the heat exchanger 101 that will communicate with the heating element of the pump housing made from highly conductive material and creating the outer half of the heat exchanger 101 from an insulative material, as one might intuit would reduce temperature loss, also creating the outer half from highly conductive material, provides further surface area and greater mass to transfer heat from the heating element or to the cooling element of the pump housing, through the heat exchanger 101, and to or from the infusion fluid. Thus, as the heating element transfers heat to the heat exchanger 101, heat is dissipated to the plurality of fins 302 from both the interior half and the outer half. Similarly, the cooling element may cool the heat exchanger by cooling the plurality of fins 302 by cooling the two halves.
The heat exchanger of the present invention can be formed from any number of thermally conductive materials, such as: cast anodized aluminum, copper, gold, silver, carbon foam, ceramics, and the like, as is known in the art. The material chosen for use in the heat exchanger of the present invention must be capable of adequate heat conduction and dispersion to ensure proper heat distribution across the surface, as well as heat transfer to or from the fluid desired to be warmed or cooled. Thermodynamics dictates that for two materials with the same specific heat, that is the amount of heat energy required to change the temperature of the material one unit per unit of mass, the material with a greater mass will more efficiently transfer heat to the material with a lesser mass. This efficiency level is often understood as thermal capacitance—in that materials with greater thermal capacitance (i.e. mass) will retain more heat while transferring energy to the adjacent material, sufficient to greatly increase the temperature of the second material, without the unwanted loss of energy. Analogizing the heat exchange occurring between the heat exchanger and the infusion fluid to be warmed by way of example, a material with a mass of 1.5 kilograms is heated to 60° Celsius and placed in close, direct contact with a material having a mass of 0.5 kilograms at a temperature of 40° Celsius. When the heating is complete, both materials will achieve a temperature of 55° Celsius. The energy stored by the hotter component, via its increased mass, allows for a better exchange of heat energy between the two materials. The converse is also true, by which the component with the increased mass is cooled. The selection of a material, given the special requirements of the present invention, therefore requires the consideration of the mass of the material, as well as the thermodynamic properties of that material.
The air-trap embodied by the present invention is capable of functioning at varying inclinations and orientations. The cylinder formed by the air-trap is between 3 inches and 10 inches in height, preferably between 3.5 inches and 7 inches, and most preferably between 4 inches and 6 inches. The diameter of the air-trap cylinder is between 0.5 inches and 2 inches, preferably 0.625 inches and 1.5 inches, and most preferably 0.75 inches and 1.25 inches. The air-trap is able to properly remove air from the fluid as it passes through, even when the air-trap is tilted off its vertical axis between 10° and 90°, though most preferably up to 45°.
Heat Exchanger and Heating and Cooling Elements
As discussed above, efficient transfer of heat, to or from the infusion fluid, to be warmed or cooled impacts the present invention. Heating infusion fluid is first described, followed by illustrative examples of cooling infusion fluid. It is appreciated that where heating by the heating element is described, a cooling element may alternatively be used to cool infusion fluid in a similar manner. The present invention's use of a wide flow, short linear travel flow pattern allows for a more turbulent flow with an extremely large contact area. The contact area being described is the area of interface between the heat exchanger and the fluid passing through. Described as a ribbon of fluid, the fluid traveling through a heat exchanger, made in accordance with the present invention, will flow in very short linear distances along the short segments of linear distance, but will instead be proportionately wider. In fact, the flow cavity created for fluid flow through the heat exchanger is wider than it is long, and longer than it is deep, thereby creating a tortuous ribbon shape for the fluid to pass through.
A heat exchanger made in accordance with the present invention creates this turbulent flow path and maintains it as the fluid flows over the fins. The fins 302, as depicted in
For temperature control, transferring heat energy to or from the heat exchanger 101 occurs at an exposure surface 225 of the heat exchanger, the portion not covered or contained within the disposable cartridge, as shown in
The exposure surface 225 of the heat exchanger, visible in
It is appreciated that while a substantially flat exposure surface 225 and a substantially flat heating platen 275 are described and illustrated in the figures herein, the exposure surface and the heating platen may be formed in other shapes. The exposure surface and the heating platen formed in other shapes, however, should still be formed so that the two are able to mate, so as to be positioned immediately next to on another and minimize the gaps between the two. Reasons for configuring the exposure surface 225 and the heating platen 275 in other than a substantially flat configuration may be for manufacturing efficiency, or to increase the exposure surface area, as well as for other reasons as are appreciated by those skilled in the art.
The disposable cartridge 100 may be removably attached to the pump housing 250 by an engaging actuator 280, as depicted in
In one embodiment, the thermal element may be a heating element 810 as described in
The resistors 830 are preferably connected, so as to limit the amount of capacitive coupling or capacitance leakage that occurs. Limiting capacitive coupling is beneficial because it reduces current leakage between the heating element 810 and the heat exchanger 101, and thus the infusion fluid, reducing the risk of causing electric shock to the patient. In a preferred embodiment, capacitance leakage for the pump device is less than 100 picofarads, and current leakage from the pump device to the patient is less than 10 microamperes, and from the pump device to a ground is less than 100 microamperes. Capacitive coupling may be reduced by creating multiple heat points, instead of a single heat point on the heating platen 275. In one exemplary embodiment, shown in
The heating platen may be constructed from aluminum alloys because they are lightweight and have high thermal conductivity. It is appreciated that other materials, known in the art as having similar mass and conductivity properties, may also be used to construct the heating platen. For example, the heating element may also be constructed from copper, gold, silver, carbon, ceramics, or the like, as is known in the art. Further, it may be preferred to harden the aluminum alloy of the heating platen to prevent substantial yielding that may result from the compressive force exerted during clamping the disposable cartridge to the pump housing.
In an alternative embodiment, such as that shown in
The thermoelectric cooler 860 may preferably be a peltier device or peltier thermoelectric cooler, as is known in the art. A peltier thermoelectric cooler 860, as may be used in the present invention, preferably includes an array of n-type and p-type semiconductors interposed between two ceramic insulators. The n-type and p-type semiconductors may be n-doped bismuth telluride and p-doped bismuth telluride pellets, respectively, or the like, as is known in the art. The thermoelectric cooler may also include a heat sink on the side opposite that interfacing with the heating platen 275, so as to efficiently remove heat from the heating platen and the cooling side of the thermoelectric cooler 860. The cooling element 850 in this embodiment may be used to cool infusion fluid to temperatures in the ranges between about 0° Celsius to about 37° Celsius, more specifically to about 4° Celsius to about 25° Celsius.
It is further appreciated that an embodiment that includes a thermoelectric cooler 860 configured as a peltier device, as described herein, may be used as a thermoelectric heat pump, so as to create a heating and cooling element. An embodiment configured in this manner, so as to include a heating and cooling element, allows for selectively heating or cooling the heat exchanger on the heat pump. As is known in the art, a peltier device can be configured to source heat, when current flows in one direction, and sink heat, when current is reversed in the opposite direction. Accordingly, a pump device configured in this manner may allow for using a single device to selectively heat or cool fluid as desired by the user.
In another embodiment including a thermoelectric cooler 860, the thermoelectric cooler may act as a thermoelectric heat pump, as is known in the art, providing a heating and cooling element for the pump device. More specifically, a thermoelectric heat pump that is a peltier device may source or sink heat, depending upon the direction of the current flow through the thermoelectric cooler. Accordingly, in an embodiment including a thermoelectric cooler/heat pump 860, the central controller may be configured to allow the user to selectively control the current flow through the heat pump, thus allowing the thermal element to create both heat points and cooling points on the heating platen 275.
Dynamic Range Motor and Pump
The pump device includes a pumping mechanism that is driven by a dynamic range motor drive assembly to pump the fluid from the fluid supply, through the heat exchanger, then to the patient. It is appreciated that other aspects, described in the present application, may provide additional functionality and paths through which the fluid may flow between the supply and the patient. The pumping mechanism may be a roller head occlusive pump. The rotating action of the pump roller head assembly imparts a directional, peristaltic motion to fluid existing in the pump loop that is contained within the pump chamber. In other embodiments, the pumping mechanism may be another type of peristaltic pump, for example, a non-circular peristaltic pump, a centrifugal pump, an impeller, or the like, as is known in the art for pumping fluids through malleable tubing. The motor drive assembly may be electronically controlled, for example, by a digital signal processing controller (DSP controller), as further described herein. In one embodiment, the pumping mechanism and motor drive assembly, in combination, are capable of delivering about 1 milliliter of fluid per hour to at least about 3000 milliliters of fluid per minute. Though, in some embodiments, the pump device may only be required to pump between 10 milliliters of fluid per hour to about 1200 milliliters of fluid per minute (e.g., during typical blood replenishment or replacement procedures), while in other embodiments the preferred range may be between 2000 milliliters and 8000 milliliters of fluid per minute (e.g., for delivery during emergency heart and lung procedures). In another embodiment the pumping mechanism and the motor drive assembly are capable of maintaining delivery of fluid at predetermined pressure ranging from about 0 mmHg to about 750 mmHg.
A motor drive assembly may be used to drive the pumping mechanism shown in
The motor 1010 and gear assembly 1030 communicate with the receiver of the pumping mechanism 1020. A coupler 1040 may be used to couple the output shaft of the gear assembly 1030 to the receiver of the pumping mechanism 1020. In one embodiment, the pumping mechanism 1020 may include a pumphead with multiple rollers, preferably three, that successively engage then release the tubing of the pump loop 104 within the pump chamber. Turning the roller heads and rollers causes occlusive pumping, as is known in the art.
The pump loop 104 preferably consists of at least one section of collapsible tubing, through which the fluid will flow upon initiation of pumping action. The pump loop tubing may have a thinner wall than other infusion tubing, allowing for easier pumping action by the roller pumphead. However, harmonies resulting from the pumping motion imparted on the pump loop tubing may cause fill and rebound cycles in the tube behavior, and thus may cause variability in flow rates or flow pressures. Thus, it may be preferable to reduce the fill and rebound behavior by controlling the length of the tubing in the pump loop 104, and thus the tension of the pump loop 104, when engaged with the pumping mechanism. Controlling the tension of the pump loop 104 effectively creates a tube having a shorter, fixed length, thus producing flow behavior more predictable than a tube having a greater length or a variable length. This may be accomplished by securing the tubing of the pump loop 104 at fixed points on the disposable cartridge, at a point or points before the portion of the tubing that engages the pump head, and at a point or points after the portion of the tubing that engages the pump head. In one embodiment, as illustrated in
The Watson-Marlow 313D pumphead (part no. 033.3401.000) is an example of a three-roller pumping mechanism, configured for use with tubing having 1.6 millimeter walls, and for providing 3 milliliter per revolution flow rate. The Cole-Parmer peroxide-cured silicon tubing (part no. K-06411-71) is an example of tubing for use in the pump loop, having an inner diameter of 6.4 millimeters and a wall thickness of 1.6 millimeters, that may be used with the pumping mechanism. It is appreciated that other pumping assemblies and tubing configurations, as are known in the art, may be used in embodiments of the present invention, such as two or four roller pumpheads or pumpheads, non-circular peristaltic pumps, centrifugal pumps, impellers or the like, as is known in the art. Additionally, the infusion tubing in the pump loop may be configured to have different tube bores and wall thicknesses. Alternative combinations of pumping mechanisms and tubing sizes will yield different flow rate ranges, as is known in the art.
The motor 1010 may be controlled by an electronic controller 1110 as is described by the functional block diagram in
The dynamic range motor drive assembly and disposable cartridge combination may provide flow rates of about 1 milliliter per hour to, at least, about 4000 milliliters per minute to satisfy the infusion needs from the low flow needs of Keep Vein Open (KVO) state to the rapid, high flow infusion of crystalloid, colloid, or blood product, including packed red blood cells. Further, in other fluid delivery uses, as described herein, the dynamic range motor drive assembly may provide flow rates between about 2000 milliliters per minute and 8000 milliliters per minute. It is appreciated that the user input may be configured so as to allow adjusting the flow rate in slight increments, as well as to allow for rapid adjustment of the flow rate. It is preferable, however, that a single selection (e.g., pressing the rate button once) will increase (or decrease) the flow rate by anywhere from approximately 5 milliliters to approximately 20 milliliters, and most preferably will increase (or decrease) the flow rate by approximately 10 milliliters. The ability to provide and control this broad range of flow rates may also be advantageously employed for infusion normothermic fluids into patients after surgery, or for treating or preventing hypothermia. Examples of fluids that may be delivered by the device are blood, crystalloid, colloid, saline, medication, any combination thereof or the like, as is known in the art. Yet another beneficial use of a broad spectrum of flow rates is the high speed delivery of irrigation fluids which may be warmed.
The dynamic range motor drive assembly may be further configured to deliver fluid at a substantially constant infusion pressure, which may be predetermined by the user between about 0 mmHg and about 750 mmHg, and preferably between about 25 mmHg and about 150 mmHg. More specifically, the user input may be configured to allow the user to select the preferred pressure around which the delivery should be maintained. For example, the user may select to infuse fluid at a constant pressure of 45 mmHg, causing the central controller to signal to the dynamic range motor drive assembly to increase the fluid flow rate until 45 mmHg of pressure is achieved. After achieving the predetermined 45 mmHg of pressure (in this example), the motor and pump mechanism may slow, so as to reduce the fluid flow, in an effort to substantially maintain the predetermined pressure. When, however, the one or more pressure sensors sense that the pressure is falling below the predetermined pressure, the central controller will cause the motor and pump mechanism to increase the flow rate, so as to increase the pressure, until it reaches the predetermined pressure again. Accordingly, by making adjustments to the flow rater the pump device is able to maintain a substantially constant pressure. It is appreciated that the adjustments to the flow rates may be minor adjustments, for example, 5-25 milliliters per minute, or may be more drastic adjustments, such as stopping flow altogether (i.e., 0 milliliters per minute). Pressure sensors contained in the disposable cartridge, such as the outflow pressure sensor, provide feedback to the control unit for proper adjustment of the DSP controller to maintain a constant pressure.
Attachment and Alignment
The components of the disposable cartridge that interface with the pump housing are advantageously arranged and designed, so as to allow simple, one-step attachment of the exchanger.
As described above, the exposure surface 225 of the heat exchanger 101 preferably mate with the heating platen 275 on the pump housing 250, so as to promote heat transfer by creating minimal air gaps between the two elements. Additionally each sensor located on the pump housing aligns and communicates with its corresponding mate on the disposable. There may also be an alignment mechanism, such as one or more guide pins 282 on the pump housing and corresponding guide receptors 284 on the disposable cartridge, to facilitate proper alignment when attaching the disposable cartridge to the pump housing. Proper mating also allows the heat exchanger temperature sensor 287 to communicate with, and accurately measure, the heat exchanger 101 temperature.
The disposable cartridge 100 may include one or more detector interfaces 230, allowing one or more sensors on the pump housing to correspondingly communicate with the infusion tubing on the cartridge. For example, a first detector interface 230 may allow the inflow bubble detector 120 and the inflow temperature sensor 260 to communicate with the infusion tubing 102, and the second detector interface 230 may allow the outflow bubble detector 112 and the outflow temperature sensor 261 to communicate with the outflow tubing 111 upon attaching the disposable cartridge to the pump housing. In one embodiment, as illustrated in
Additionally, the primary inflow tube 102 and the primary outflow tube 111 may be lubricated, formed from a lubricious material or the receptacles on the pump housing may be lubricated, so as to facilitate the mating between the infusion tubing and the inflow and outflow bubble detectors 120, 112 and the inflow and outflow temperature sensors 260, 261. Alternatively, the inflow and outflow temperature sensors 260, 261 and the inflow and outflow bubble detectors 120, 112 may be lubricated on their interior surfaces that engage and mate with the infusion tubing. The lubricant may be a heat resistant compound, such as silicone, or the like, as is known in the art. Furthermore, an energy transmitting material may be applied to either the infusion tubing and/or the bubble detectors 120, 112 and the temperature sensors 260, 261 to facilitate the transmission of energy from the sensor to the infusion tubing and fluid contained therein. For example, for ultrasonic-based sensors, a silicone based material may be used to facilitate transmission of sound energy. Alternatively, when including laser-based sensors, a non-refractive material may be used to facilitate the transmission of light energy.
The disposable cartridge may include one or more flow limiting interfaces 235 that align with one or more flow limiting mechanisms, which are used to restrict the flow of air or fluid through the infusion tubing at the position of the one or more flow limiting interfaces. For example, two flow limiting interfaces 235 may be formed as apertures on the disposable cartridge 100 and may allow for the fluid outflow flow limiting mechanism 240 and the air output flow limiting mechanism 241 to extend therethrough and engage the outflow tubing 111 and the air output tubing 108, shown in
There may be one or more pressure sensors on the pump housing that communicate with pressure receptors on the disposable cartridge. In one embodiment, an inflow pressure sensor 270, a pump outflow pressure sensor 271, and a fluid outflow pressure sensor 272 extend through an inflow receptor 295, a pump outflow receptor 296, and a fluid outflow receptor 297, respectively. The pressure sensors may be, in one embodiment, sensor needles, and the pressure receptors may be orifices that receive the sensor needles. Upon attachment, the pressure sensors 270, 271, 272, by way of the pressure receptors 295, 296, 297, are in communication with the inflow, pump outflow, and fluid outflow pressure junctions 103, 105, 135 of the disposable cartridge. By extending into the pressure receptors 295, 296, 297, the pressure sensors 270, 271, 272 may open a check valve therein and communicate with a captured volume of gas (e.g., the first air chamber 151) between the pressure sensor and the fluid flowing through the infusion tubing, whereby the pressure of the captured volume of gas is directly related to the fluid pressure in the associated infusion tubing. This pressure may be sensed by pressure transducers in the pump housing in communication with each of the pressure sensors. In the embodiment, the pressure receptors may extend from the disposable cartridge and have an orifice, approximately the same, or preferably a slightly smaller, diameter as the outer diameter of the pressure sensors, through which the pressure sensors extend. The pressure receptors may be constructed from a polymer material that is pliable, so as to provide a tight seal around the pressure sensors, such as silicone, a silicone compound, or the like, as is known in the art. Further, in this embodiment, each pressure receptor may include a collar 292 extending from the disposable cartridge and surround the outside diameter of each of the pressure receptors. The collars 292 may be constructed from a hard material, such as a plastic, a metal, a composite, or the like and may preferably be constructed from the same material as the cartridge from where the collars 292 extend. The collars 292 are included to prevent deformation of the pressure receptors, and to prevent the pressure receptors from separating from the pressure sensors when under high pressures, thereby allowing for continued accurate pressure monitoring. It is appreciated that, in other embodiments, the pressure sensors may not have a needle configuration, thus there may be no need for the receptors to have an orifice. Accordingly, the pressure sensors, described herein, are exemplary, and any other pressure sensors, as are known in the art, may be used.
There may be one or more sensors on the pump housing 250 that may align with one or more points on the air-trap. These sensors may detect the fluid level at the one or more points on the air-trap. The sensors may be ultrasonic sensors, optical sensor, such as a laser, or the like, as is known in the art for detecting differences in material properties. In one embodiment, the air-trap includes the lower level sensor interface 506 and the upper level sensor interface 507, as described above, in reference to
It is appreciated that the pump device and/or cartridge may contain other sensing devices than those previously described. For example, one or more blood sensors may be included on the pump housing to interface with one or more points on the infusion tubing, so as to monitor properties of blood flowing therethrough. The blood sensor may be an optical-based sensor, such as a raman laser, or the like, as is known in the art. The blood sensor may monitor blood properties or blood chemistry such as, but not limited to: blood hematology, electrolytes, enzymes, blood gasses, clotting indices, and glucose levels. Other blood chemistry characteristics may likewise be monitored or sensed, as is known in the art. Another example of an additional sensor that may be included in the pump device is a flow sensor. The flow sensor may be an ultrasonic sensor, an optical-based sensor, such as a laser sensor, a thermal sensor, or the like, as is known in the art.
Accordingly, each of the components described above properly align and engage with the pump housing upon attachment. To align the disposable cartridge 100 to the pump housing 250, the clamping mechanisms 290 of the pump housing shall be aligned with the attachment points 210 on the disposable. By aligning the clamping mechanisms 290 with the attachment points 210, the individual components are directly aligned with their complimentary mate. Alignment mechanisms, such as the one or more guide pins 282 on the pump housing and the corresponding guide receptors 284 on the disposable cartridge, may also be included to facilitate proper alignment when attaching the disposable cartridge to the pump housing. The guide receptors 284 may be configured as apertures having a diameter corresponding to that of the one or more guide pins 282. Closing the engaging actuator 280 will cause the clamping mechanisms 290 to pull the attachment points 210, and therefore the disposable, to mate with the pump housing, and to interconnect each component pair. Furthermore, the pump housing 250 may include an install detector that determines whether the disposable cartridge 100 is properly aligned and attached. The install detector may be one or more switches that are tripped upon successfully attaching the disposable to the pump housing. The pump device may be configured to generate an alert or an alarm if the user attempts to begin operation without the install detector being tripped, or it may alternatively be configured to not power on or begin pumping unless the install detector has been properly tripped.
User Input and Control
The pump device allows user control through a simple user interface that offers easy access to primary functions by requiring minimal input selections by a user.
Certain aspects of the present application reference block diagrams of systems, methods, and apparatuses, according to at least one embodiment described herein. It will be understood that each block of the block diagrams, and combinations of blocks in the block diagrams, respectively, can be implemented, at least partially, by computer program instructions, generally referenced herein as the central controller 11100. These computer program instructions may be loaded onto a general purpose computer, special purpose computer, special purpose hardware-based computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute on the computer or other programmable data processing apparatus, create means for implementing the functionality of each block of the block diagrams, or combinations of blocks in the block diagrams, discussed in detail in the descriptions below.
The user interface control panel 1200 may include power input 1210 that turns the infusion device on, if it is not already on. If the device is already on, selecting the power input 1210 may cause the machine to go into standby mode if it is plugged in, or may turn off the infusion device if it is running on batteries or any other alternative power means. A prime input 1220 allows the user to select either manual prime, by continuously depressing the prime input 1220 for the duration for which priming is desired, or automatic prime, by selecting and releasing the prime input 1220. More details regarding the prime sequences are discussed below in reference to
One or more maximum pressure inputs 1240 may allow the user to select the maximum pressure tolerated in the infusion tubing. For example, the pump device may include two maximum pressure inputs 1240, such as 100 mmHg and 300 mmHg, and if one or more of the pressure sensors sense a pressure exceeding the pressure level corresponding to the maximum pressure input 1240 selected, the device may reduce the flow rate, or stop pumping fluid and alert the user of the excessive pressure in the system. For example, during operation, if a flow rate of 500 milliliters per minute and a maximum of 100 mmHg is selected, the device will increase the flow rate until 500 milliliters per minute is achieved, unless the pressure reaches or exceeds 100 mmHg. If the pressure reaches or exceeds the selected limit, the device will slow the flow rate so as to allow the pressure to drop. After the pressure drops, the device will increase the flow rate again until the flow rate is reached, repeating the cycle until the selected flow rate is achieved without exceeding the pressure maximum. Similarly, the pump device may include a pressure increase input 1242 and a pressure decrease input 1244, by which the user may pre-define a pressure to be maintained by the pump device. The pump device may further include one or more preset pressure inputs, which will allow the device to maintain the flow pressure corresponding to the pressure preset selected. The pressure maintenance level may be displayed in a selected pressure indicator 1246. An actual pressure indicator 1248 may display the actual pressure during operation. Using the pressure increase input 1242 and the pressure decrease input 1244 will allow the device to pump fluid at a substantially constant pressure. For example, the infusion device may pump fluids maintaining the pressure between a range of about 0 mmHg and about 750 mmHg, and more preferably between about 25 mmHg and about 150 mmHg. For example, the user may select the pressure increase input 1242 until 45 mmHg is displayed in the selected pressure input 1246. During operation in this example, the dynamic range motor drive assembly will adjust the fluid flow rate to maintain, within a reasonable tolerance, for example, within 5%-20% of the selected pressure, a 45 mmHg pressure reading at the outflow pressure sensor.
A standard infusion input 1250, a rapid infusion input 1260, and a group of bolus preset inputs 1270 allow a user to select the infusion mode of the device. Selecting the standard infusion input 1250 will cause the device to pump fluid at a predetermined rate. For example, the device may, by default, pump 120 milliliters per hour when the standard infusion input 1250 is depressed. Similarly, selecting the rapid infusion input 1260 may cause the device to pump at a predetermined rate faster than the standard infusion, for example 500 milliliters per minute. The bolus preset inputs 1270 may include one or more buttons that, when selected, cause the infusion device to deliver a predetermined volume, for example, 100, 250, 500, or 1000 milliliters, of fluid at a predetermined rate, for example, at 500 milliliters per minute. The predetermined rate for each of the standard, rapid, and bolus infusion modes may be altered by the user by depressing the rate increase input 1280 or rate decrease input 1281. The rate increase and decrease inputs 1280, 1281 preferably only cause a small increment or decrement in the infusion rates, for example, between approximately 1 milliliter and 50 milliliters, preferably approximately 10 milliliters, each time the buttons are depressed. This allows a simple, but precise, control over the flow rates. Additionally, it may be preferable to also allow for a rapid rate increment or decrement when the rate increase and decrease inputs 1280,1281 are depressed and held. For example, if the rate increase input 1280 is held, the infusion rate may increase between approximately 10 and 500 milliliter increments or decrements, preferably approximately 50 milliliter increments, instead of 5 or 10 milliliters.
Depressing the start input 1285 will cause the pump device to begin operation in the selected mode. Similarly, the stop input 1286 will cause the pump device to stop delivering fluid. Additionally, it may be advantageous that the operation of the device, and the signals being sent from the above-discussed sensors, can be monitored so as to halt operation while unwanted behavior is encountered. For example, if the outflow bubble detector 112 senses air in the infusion tubing, a signal should be sent to the central controller to halt operation and signal to the user the nature of the problem encountered. Another example would be the outflow temperature sensor 140 detecting temperatures less than the desired temperature, thus causing the central controller to stop infusion and alert the user as to an error with the heat exchanger. Other examples of operating behavior that may cause an alarm and/or halt the device operation are, but not limited to: battery levels, excessive volume infused, motor failure, disposable not properly attached, pressure failures, computer/control unit failure, infusion line occlusion, and pump failure. It should be appreciated that the foregoing examples are for illustrative purposes, and that many other sensors and error handling routines may be implemented in the present invention, so as to at least cause a signal to be sent to the user and possibly to halt the operation of the device.
The user interface control panel 1200 may also cause indicators to be displayed showing the state in which the pump device is operating and certain selected parameters. For example, LED indicators may be mated with each of the above exemplary input options, so as to indicate which inputs have been selected. This gives the user a quick indication of the state in which pump device is operating. Additionally, there may be a selected rate indicator 1290, an actual rate indicator 1291, a selected pressure indicator 1246, and an actual pressure indicator 1248 that display to the user the flow rate and pressure selected by the user, and the actual flow rate and pressure of the device, respectively. These displays may be LED indicators, liquid crystal display indicators, or the like, as is known in the art. It is appreciated that other alerting mechanisms, such as beeps, alarms, tones, verbal warnings, or the like, as is known in the art, may be used by the present invention to indicate certain conditions and the severity thereof.
There may optionally be another status display panel 1205, in which the current operating data and any existing alarm indicators may be displayed, as also shown in
Before entering into an infusion mode, the pump device is preferably primed. The pump device may be primed either automatically or manually.
The pump device operates to maintain the heat exchanger at a predetermined temperature, which may be sensed by the heat exchanger temperature sensor 287, as shown in block 1610, and further described in reference to
In addition to maintaining the heat exchanger at the predetermined temperature, the central controller also takes into consideration the flow rate. At block 1620, the central controller receives the calculated flow rate of the infusion fluid from the dynamic range motor drive assembly, as further discussed in reference to
At block 1630, the central controller receives from the inflow temperature sensor 260, as further discussed in reference to
Thus, as occurs at block 1640, the central controller may consider at least one or a combination of the heat exchanger temperature, the inflow temperature, and the flow rate to cause proper adjustments in the heating element 810 or cooling element 850. For example, the greater the flow rates, the quicker the central controller adjusts to heat or cool to keep up with the flow rates. When the flow rates are slower, smaller adjustments are made by the central controller. Similarly, for greater temperature differences, the infusion fluid will have to be warmed, or cooled, at a higher, or Tower, heat energy. The device configured in this embodiment may be used to heat infusion fluid to temperatures in the ranges from about 35° Celsius to about 50° Celsius, more specifically from about 37° Celsius to about 43° Celsius. The device configured in this embodiment may be used to cool infusion fluid to temperatures in the ranges from about 0° Celsius to about 37° Celsius, more specifically from about 4° Celsius to about 25° Celsius.
Example—Warming Fluid and Pumping at Variable Flow Rates
An embodiment of the infusion system under the present invention is shown in
For the purposes of this Example, the fluid being infused into the patient is blood (although a similarly configured pump system may be used to deliver colloid, crystalloid, saline, medication, or the like). The fluid entering the pump system, embodied in this Example, may be around 20° Celsius. The rate at which infusion is conducted is about 1000 milliliters per minute. However, being driven by a motor, and controlled by an electronic controller, preferably a DSP controller, the rapid infusion system may be capable of pumping fluid at a rate of about 10 milliliters per hour to at least about 1200 milliliters per minute. Low speed operation could be used for routine IV (intra-venous) infusion; and high speed operation would be used for rapid fluid infusion for cases such as emergency room trauma. Additionally, the device can be particularly advantageous in situations where it may be preferable to first employ routine IV infusion, followed by rapid infusion, followed again by routine infusion, such as during a transplant operation. It is also appreciated that in some embodiments, for example during emergency heart and lung support procedures, it may be preferable to infuse blood at rates as great as about, 2000 milliliters per minute to about 8000 milliliters per minute.
Conventional IV fluid, or blood bags or bottles, can be used, for example, or an alternate fluid reservoir can be employed, particularly when large quantities are to be infused. The bags or bottles are spiked with a delivery tubing that is connected to the disposable cartridge. The disposable cartridge is aligned and attached to the front of the pump housing, with pumping mechanism extending through the attached disposable cartridge, and communicating with the pump loop.
After the disposable cartridge 100 is attached to the pump housing 250, aligning and engaging each of the cartridge components and sensors with their mates, the roller pumphead of the pumping mechanism may apply pumping pressure to the pump loop 104, causing fluid to flow from a fluid source through the cartridge, and infusing at the desired rate.
The user may turn the pump device on by depressing the power input 1210. Next, after turning on, and before infusing fluid, the device shall be primed. The user may use automatic priming by selecting the prime input 1220, or the user may prefer to hold down the prime input 1220 so as to cause the device to be manually primed for as long as the user holds down the device. Priming is successful after air has been purged from the fluid path, and substantially all the way to the end of the patient outflow line, by automatic or manual priming. The user may then choose to either infuse at a standard adjustable rate by selecting the standard infusion input 1250, infuse a bolus of either 100 milliliters, 250 milliliters, 500 milliliters, or 1000 milliliters at an adjustable rate initially set to 500 milliliters per minute, by selecting one of the bolus preset inputs 1270, or infuse at a rapid adjustable rapid rate by selecting the rapid infusion input 1260. In one embodiment, the heat is on in the default setting; thus the user does not have to select anything to begin heating the fluid. Accordingly, the user may turn off the heating mode by deselecting the heat input 1230. Alternatively, in another embodiment, the heat may not be set to on in the default setting and the user thus may turn the heating mode on by selecting the heat input 1230, and similarly turn it off by selecting it again (or deselecting it). After the device is primed and the desired infusion mode and infusion rates are set, infusion begins when the user selects the start input 1285. The user may vary the infusion rate by selecting the rate increase input 1280 or rate decrease input 1281, which causes the electronic controller to advantageously increase or decrease the pump rate accurately to the selected, or default, infusion rate. Upon receipt of the signal from the user interface, for example, for rapid infusion with an increased rate of 1000 milliliters per minute, the electronic controller 1110 sets its PWM signal duty cycle for transmission to the motor power drive circuitry 1120, to turn the motor drive assembly at the appropriate speed. For example, to achieve a 1000 milliliter per minute flow rate with a pumping mechanism 1020 that provides 3 milliliters of fluid per revolution and a motor that is connected to a 14:1 gear assembly 1030, the motor needs to turn at 4667 revolutions per minute.
While pumping under this scenario, LED indicators would be powered next to the rapid infusion input, the chosen maximum pressure input, and the heat input on the user interface panel 1200. Additionally, the selected rate indicator 1290 would display 1000, and the actual rate indicator 1291 would display the rate the infusion device is actually pumping. Similarly, the status display panel 1205 may indicate that the device is operating in rapid infusion mode, the heat is on, the sensed temperature of the blood, the sensed pressure of the blood in the infusion tubing, as well as the total volume infused.
Again, referring to
The inflow pressure junction 103 monitors negative pressure, in the event that fluid remains within the disposable cartridge but is not flowing in the direction of the patient. Such a circumstance could arise if the fluid source bag collapses, yet fluid remains in the cartridge. If the pressure at the inflow pressure junction 103 falls below a predetermined pressure, for example, approximately 1 mmHg, then the pump may stop pumping.
When the blood leaves the pump loop 104, it flows through a second t-junction, which serves as the pump outflow pressure junction 105. The pump outflow pressure junction 105, in combination with another air chamber and the pump outflow pressure sensor 271, determines the pressure of the blood as it exits the pump loop 104, so that the flow of the blood through the disposable cartridge 100 can be regulated. The pump outflow pressure junction measures the pressure of the fluid proceeding through the cartridge. Here, blockage is monitored, so that when the pressure exceeds a predetermined pressure, for example, approximately 500 mmHg, the pump may shut down to avoid damage.
The blood then passes into the heat exchanger 101 via the exchanger inlet port 106. The heat exchanger 101 of this Example is created from two halves, as depicted in
When a disposable cartridge according to the present invention is used, the effective exchange of heat, from the heat exchanger to the fluid being infused, achieves the appropriate rise in temperature of the fluid, without having to expose the fluid to potentially dangerous temperatures, as defined as a predetermined temperature limit. Instead of having regions of varied temperature, to which the blood or fluid is exposed, the heat exchanger's constant temperature allows for more efficient transfer of heat energy to the blood. At a flow rate of 1000 milliliters per minute, achieving a fluid exit temperature of 37° Celsius means never having to expose the blood to temperatures which could be deleterious to the fluid being infused. In fact, using anodized aluminum yielded a 95-96% efficiency in transferring heat energy to blood, sufficient to generate a 17° Celsius rise in temperature.
Once the blood enters the heat exchanger, the blood fills the flow cavity 304 before proceeding to traverse the entirety of the heat exchanger. The blood fills the flow cavity first, because of the narrower flow area created by the flow fin 303 which defines the flow cavity. By creating a smaller flow path to flow over the first fin, as depicted in
The fins used in the heat exchanger, described in
Once the blood flow reaches the top of the heat exchanger, it exits via the exchanger outlet port 107 located a position opposite the exchanger inlet port 106 of the heat exchanger 101. At this point, the fluid for infusion has undergone warming and the desired temperature has been reached. The heat exchanger temperature sensor 287 measures the temperature of the heat exchanger 101 and provides feedback to the central controller for effective temperature regulation. The blood then enters the air-trap 110 at a location approximately midway between the top and bottom of the long-axis of the air-trap 110. In this Example, the air-trap is about 4.2 inches along its long, vertical axis and about 1 inch in diameter. The air-trap intake port 503 is located about 2.1 inches from the bottom of the air-trap (see
Air may become trapped in the blood in this Example via several mechanisms. Through spiking the blood, as it is attached to the pump system for infusion, trapping air and in essence failing to properly purge the source of the blood before attachment to the system. Also, the heating of the fluid itself can cause the release of stored gas within the blood, which may be deleterious if introduced into the patient.
As the amount of air in the air-trap 110 increases, the level of blood in this Example, lowers within the air-trap. When the blood is below the upper level sensor interface 507 and the lower level sensor interface 506, which, in this Example, are ultrasonic sensors that communicate with the upper level sensor 246 and the lower level sensor 245, respectively, in the pump housing the level of fluid in the air-trap, the valve at the fluid output port 505 closes. When the fluid outflow flow limiting mechanism 240 is closed, compressing the primary outflow tube 108, the air output flow limiting mechanism 241 is open. This increases the blood volume in the air-trap, forcing air out of the air output port 504. The lower level and upper level ultrasonic sensors 245,246 are located in the pump housing 250. The ultrasonic sensors utilize energy transmitting material, for example, silicone or urethane pads, to facilitate the transmission of the sensor signals to the lower level sensor interface 506 and the upper level sensor interface 507, in order to effectively couple and measure the level of fluid within the air-trap. When the level of blood rises to or above the upper level sensor interface 507, and thus also above the lower level sensor interface 506, the air output flow limiting mechanism 241 closes. At approximately the same time that the air output flow limiting mechanism 241 closes, the fluid outflow flow limiting mechanism 240 opens, and blood exits the air-trap and proceeds toward the patient.
In this Example, the fluid then passes through the fluid outflow pressure junction 135, which assists in determining the pressure for controlling the flow within the cartridge when based on pressure. If there is blockage, and the pressure begins to rise, this device will try to keep the pressure within an acceptable range, which can be between approximately 0 mmHg and the predetermined upper limit, which in this Example may be either 100 mmHg or 300 mmHg, depending upon what is selected by the user, by adjusting the flow rates. For example, during operation, the central controller will cause the dynamic range motor drive assembly to pump fluid to achieve the pre-selected rate by the user. However, if the pressure limit is reached, the dynamic range motor drive assembly will slow, allowing the pressure to fall and then speed up again to reach the rate. If the pressure at the fluid outflow pressure junction 135 rises above a predetermined safety level, possibly different than that level selectable by the user, for example, 500 mmHg the pump may shut down.
In the present Example, however, before blood reaches the patient, it passes through the outflow bubble detector 112. The outflow bubble detector analyzes the blood on its way to the patient to determine that the air-trap removed potentially deleterious air from the system. The bubble detector in this Example uses an ultrasonic sensor, which sends a signal across the tube. Any air bubbles present in the system will attenuate the signal. The system will shut the pump down if bubbles as small as 30 to 50 microliters are detected. The system is able to detect bubbles of this size at the maximum flow rate of, for example, 1200 milliliters per minute (in the intravenous fluid infusion example).
After passing through the outflow bubble detector 112, the fluid outflow temperature sensor 261 uses infrared temperature detection to measure the temperature of the blood before being delivered to the patient. This allows for a final temperature verification of the fluid (e.g., the blood), so as to avoid delivering overheated fluid to the patient.
Finally, after infusion, the disposable cartridge 100 may be removed from the pump housing 250 and may be discarded. A new disposable cartridge 100 may then be attached to the same pump housing 250 for subsequent use. The disposability of the heat exchanger is beneficial in settings in which quick turn-around is necessary between uses, by avoiding sterilization after each use. Also, the disposable cartridge of the present invention, being a self-contained heating device, promotes a sterile surgical field, by removing external heating mechanisms and avoiding the introduction of unnecessary foreign fluids.
Unlike standard or traditional methods of intravenous fluid administration, the rapid infusion system described herein can provide continuous total replacement of adult human blood volume through virtually any sort of hemorrhage, for an indefinite period of time, and can rapidly regulate fluid temperature with minimal increase in resistance to flow. Additionally, the device can easily and rapidly administer massive quantities of blood to a single patient during a single operation, administer physiologic fluid maintained at a predetermined temperature, at flow rates as great as 1200 milliliters per minute (or greater in other examples), and permit simultaneous display and control of fluid temperature. The system can easily be carried, and is able to be quickly and easily used in emergency situations or by emergency personnel in the field. The system can be configured to infuse an infinite amount of blood over an indefinite period of time, based on the pump assembly employed, the tubing sizes, etc., employed.
Further, the system described in this Example may be used to infuse blood at a temperature greater than the patient's body temperature, as is advantageous in certain therapies, such as during the treatments of viruses, for example, the hepatitis C virus. In an embodiment used to warm blood for therapeutic effects, such as systemic warming during the treatment of the hepatitis C virus, the blood may be warmed to temperatures between about 37° Celsius and about 48° Celsius prior to infusion to the patient. This procedure may be repeated one or more times, allowing the patient to cool in between each successive infusion of warmed blood. The infusion target for warming the patient may be generally directed for systemic warming of the patient's core, or, alternatively, warming may be targeted to a specific region or organ, such as, for example, the liver.
If desired, the present invention can include multiple pumps infusing fluid to a patient through multiple catheters, thereby providing such fluids to the patient in volumes which far exceed that possible by present infusion systems.
In another embodiment, the pump device may be used to cool, rather than warm, blood or other fluid being delivered to a patient. This may be particularly useful for patients suffering from an acute stroke, for example, to controllably induce hypothermia by cooling the infused blood. This embodiment operates much like the embodiment described in the previous example, except that it includes a cooling element 850, as shown in
In this embodiment, the cooling element 850 cools the heat exchanger 101, including the plurality of fins housed therein, to a temperature lower than its ambient temperature before infusion. The infusion device of this embodiment may cool infusion fluid to temperatures between about 0° Celsius and about 37° Celsius, more preferably between about 4° Celsius and about 25° Celsius. In this example, blood is cooled to, and maintained at, a temperature of about 20° Celsius while flowing through the heat exchanger 101. After continuing through the same flow path through the entire disposable cartridge, the cooled blood is then infused to the patient, for example, to the brain region. Note, however, that cooled blood, or other infusion fluids, may be infused to other regions of a patient, which will similarly induce a controlled hypothermia. In another example, cooled blood may be intravenously infused to a region near the heart for a patient suffering from an acute myocardial infarction.
In one variation of this embodiment, the pump device may contain a heating element 810 and a cooling element 850 both, as described by this example. The disposable cartridge may be attached to the pump housing, so as to align with the heating element 810, or the disposable cartridge may be attached to the pump housing, so as to align with the cooling element 850. Thus, in this configuration, the pump device may be controlled so as to allow the user to either deliver warm or cool blood during operation. This configuration would be advantageous for procedures that benefit from interchangeably delivering volumes of warmed blood and cooled blood, or for warming blood to a desired temperature, for example, 43° Celsius, and then cooling back to body temperature (i.e., 37° Celsius), or vice versa. It is further appreciated that a second disposable cartridge, or a single disposable cartridge with a second heat exchanger, may be included with the pump system, with one heat exchanger delivering warmed fluid and another delivering cooled fluid.
In yet another variation, the pump device may have an interchangeable heating element and cooling element. In this configuration, the cooling element, including the thermoelectric coolers, heating platen, and thermal pad, can replace, at will, the heating element, including the power insulators, power resistors, beating platen, and thermal pad. It is appreciated that only the assembly housing the power insulators and power resistors, and the assembly housing the thermoelectric coolers may be removable, leaving the heating platen and thermal pad remaining in the pump housing. This interchangeable configuration is advantageous because it allows for rapid switching between providing cooling and warming capabilities while still maintaining the small size that beneficially allows simple operation.
Example—Body Temperature Regulation
In yet another embodiment, the pump device may be used to deliver large quantities of fluid in a controlled manner, and at a controlled temperature, through the body to assist in controlling the patient's core body temperature. Certain procedures benefit from, or are positively affected by, controllably inducing hypothermia.
In one example, saline solution is pumped through the heat exchanger including a cooling element 850, as in the previous example, for ultimate delivery to a patient suffering from an acute myocardial infarction. The saline solution may initially be stored at room temperature, for example, about 20° Celsius to about 22° Celsius, and is preferably cooled between about 0° Celsius and about 15° Celsius. In this example, saline is cooled, for example, to about 10° Celsius prior to infusion. The cooled saline solution is then delivered to the patient's bladder using a catheter. A double lumen or triple lumen catheter may be used for delivering cooled saline therethrough, and into the bladder and replacing previously delivered fluid by evacuation through the catheter. In this example, the patient's bladder is cooled because it has a relatively large volume and is centrally located, providing a quicker, and more controlled means to cool one's core temperature.
In another variation, the saline solution may be warmed, instead of cooled, using a heating element in the pump housing, as in the first example above. Delivering warmed fluid into a centrally located volume may be helpful, for example, when a patient is recovering from a surgical procedure under anesthesia, or when a patient is suffering from extreme hypothermia.
Alternatively, rather than utilizing the cooling or warming capabilities of the pump device, pre-cooled or pre-warmed fluid may be delivered to cool or warm a patient's core temperature. In this embodiment, the pump device is beneficial for controlling the flow rates and pressures, including the ability to deliver pre-warmed or pre-cooled fluids at a wide range of flow rates. Controlling the flow rates will further allow more precise control of the patient's core temperature.
It is appreciated that, in this embodiment, sensing and preventing air in the fluid path is unnecessary. The bubble detectors and air-trap may be disabled while the device is used in this embodiment.
In yet another embodiment, the pump device may be operated as in any of the previous examples, however, the pump device may maintain a substantially consistent flow pressure. The pump device in this embodiment may maintain a relatively constant pressure, between a range of about 0 mmHg and about 750 mmHg, and more preferably between about 25 mmHg and about 150 mmHg. This embodiment is particularly advantageous during certain surgical procedures, such as endoscopic procedures, like arthroscopic or laparoscopic surgeries. During an arthroscopic surgery, for example, it is desirable to deliver fluid to expand the joint, as well as to flush the surgical area and to tamponade bleeding vessels. It may also be desirable to warm the fluid to avoid unnecessary cooling of the surgical region.
Saline solution may be used as the fluid delivered in this embodiment. Each of the steps described in the first example to prepare the pump device for operation, such as attaching the disposable cartridge and selecting the desired inputs, are carried out. However, under this embodiment, the user preferably selects either the pressure increase input 1242, or the pressure decrease input 1244, on the user interface panel 1200 to pre-select the desired flow pressure maintenance level. Upon selecting one of the pressure inputs, the selected pressure indicator 1246 displays the pressure selected. In this example, the user selects the pressure increase input 1242 until 45 mmHg is displayed on the selected pressure indicator 1246. Additionally, the user may select the heat input 1230 to cause the saline solution to be warmed while circulating through the heat exchanger 101 prior to delivery to the patient. Finally, the primary outflow tube 111 is connected, via surgical tubing, such as silicon tubing, to an inflow cannula, or the like, as is typically used during arthroscopic or laparoscopic procedures. The cannula is inserted into the patient at or near the joint to allow accurately controlling the delivery of the fluid.
Upon beginning operation, the pump device generally operates as described in the first example, warming the saline solution prior to delivery via the cannula to the patient. However, the pressure may be substantially maintained at a selected pressure—here 45 mmHg—by the device central controller 1100, causing the electronic controller 1110 to adjust the motor speed, thus adjusting the flow rate to substantially maintain a flow pressure of 45 mmHg at the pre-selected desired flow rate. A feedback loop exists from the fluid outflow pressure junction 135 to the dynamic motor drive assembly, via the device central controller 1100, which will allow continuous adjustments to be made to the dynamic motor drive assembly to maintain the constant pressure. It is further appreciated that during operation, the pressure maintenance levels may be changed by selecting one of the pressure increase input 1242 or the pressure decrease input 1244. The device used in this embodiment may preferably deliver flow rates between about 0 milliliters per minute to about 2000 milliliters per minute.
Example—Cardiopulmonary Bypass or Assist
In yet another embodiment, the pump device described herein may be used with patients undergoing cardiotomy, and requiring at least partial cardiopulmonary bypass or suffering from organ (heart and/or lung) failure or deterioration. The device used in this embodiment may maintain blood circulation while preferably oxygenating the blood prior to infusion (or re-infusion). Examples of uses for which a device configured for this embodiment may be used are to provide cardiac bypass during cardiac surgery, cardiac assist, extra-corporeal membrane oxygenation during percutaneous heart valve replacement procedures, or during the treatment of pneumonia, sepsis (treating and/or supporting resulting organ failure), acute respiratory distress syndrome, emphysema, chronic bronchitis, asthma with status asthmaticus, neonatal respiratory distress syndrome, smoke inhalation, or burn victims (treating and/or supporting resulting organ failure).
A device configured for use in this embodiment may include a pumping mechanism, a dynamic range motor drive assembly, and a central controller, as described herein. Further, the device preferably includes an oxygenator in line with the infusion path. The fluid flow circuit may preferably be configured as a closed circuit, whereby blood is drawn from the patient, pumped through the pump device, pumped through the oxygenator, and then re-infused to the patient. The oxygenator may be placed distal to the dynamic range motor drive assembly prior to infusion to the patient. The oxygenator may be a bubble oxygenator, a membrane oxygenator having multiple capillary tubes creating membranes between the blood and the gas, or the like, as is known in the art. The pumping mechanism may be a roller head occlusive pump, a non-circular peristaltic pump, a centrifugal or conical pump, an impeller, or the like, as is known in the art. The dynamic range motor drive assembly, the pumping mechanism, and the electronic controller are preferably configured, so as to provide infusion flow rates up to at least 8000 milliliters per minute, preferably between about 2000 milliliters per minute and about 4000 milliliters per minute. It is appreciated that a pump device, configured for cardiopulmonary bypass or assist, may also be able to deliver fluids to a patient at slower flow rates, like those described above, such as flow rates as low as 1 milliliter per hour. The infusion flow pressure may also be monitored and controlled as described above. The pump device may also include an air-trap, so as to capture bubbles in the blood before infusion, and a thermal element, such as a heating element and/or a cooling element, as described above, so as to allow cooling or heating the blood prior to oxygenation and delivery to the patient. A pump device used in this embodiment is particularly advantageous because of its manageable size and simple operation, while allowing a wide range of infusion flow rates.
In yet another embodiment, the pump device, described herein, may be used during renal replacement therapy, such as kidney dialysis, to treat patients with renal impairment or failure. Accordingly, this embodiment may be used to circulate cleansed or filtered blood through a patient.
A device configured for use in this embodiment may include at least two pumping mechanisms, at least two dynamic range motor drive assemblies, a central controller, and a dialysate bath. Accordingly, the blood may be pumped by one pumping mechanism and motor drive assembly through multiple capillary tubes, forming a semi-permeable membrane between the dialysate bath and the blood, as is known in the art. The dialysate may be pumped by another pumping mechanism and motor drive assembly across the capillary tubes in a direction opposite of the direction the blood is pumped through the capillary tubes, so as to create a counter current bath of osmotic fluid. The osmotic fluid or dialysate may include the same, or higher, levels of physiologic electrolytes, such as salts, as normally exist in blood, so as to force undesired solutes from the blood to the dialysate through osmosis. Further, the dialysate may include higher levels of bicarbonate than normally exist in the blood, so as to force bicarbonates from the dialysate to the blood, thereby reducing acidosis, if so desired. The blood flow circuit may preferably be configured as a closed circuit, whereby blood is drawn from the patient, pumped through the pump device, pumped through the dialysate bath, and then re-infused to the patient. The dialysate bath may be configured as a closed circuit or an open circuit, allowing for reuse of the dialysate, or for replenishing used dialysate with fresh dialysate, so as to maintain consistent electrolyte concentrations. A device configured for use in this embodiment may provide simple infusion flow rate control over the entire range, as disclosed herein, as well as simple dialysate bath flow rate control. The infusion flow rate may preferably range from about 200 milliliters per minute to about 700 milliliters per minute, more preferably from about 300 milliliters per minute to about 500 milliliters per minute. Though, it is appreciated that a pump device configured for dialysis procedures may also be able to deliver fluids to a patient at slower flow rates, such as 1 milliliter per hour, or faster flow rates, such as up to 8000 milliliters per minute, as further described herein. Similarly, the flow pressure of both the dialysate and the blood infusion may also be controlled as described herein. Like described above, the device may also include an air-trap and a thermal element, such as a heating and/or cooling element. A pump device configured for use during dialysis procedures is particularly advantageous because of its portability, relative low cost, ease of use, and its robust features such as variable flow rates, heating and/or cooling, and utilizing an active air-trap.
The above description is intended to be illustrative and not restrictive. Many embodiments will be apparent to those of skill in the art upon reading the above description. The scope of the invention should therefore be determined not with reference to the above description, but should instead be determined with reference to the appended Claims, along with the full scope of equivalents to which such Claims are entitled. The disclosures of all articles and references referred to herein, including patents, patent applications, and publications, are incorporated herein by reference.